Iol with varying correction of chromatic aberration

ABSTRACT

An ophthalmic lens includes an optical filter operable to filter out at least visible light having a wavelength less than 450 nm. The lens also includes a first diffractive structure adapted to produce a focus for visible light in a first wavelength range above 550 nm and to reduce longitudinal chromatic aberration to less than one diopter for incoming visible light in the first wavelength range. The lens also includes a second diffractive structure outside the first diffractive structure in a radial direction and adapted to produce a focus for visible light in a second wavelength range between 450 nm and 550 nm. The second diffractive structure is also adapted to reduce longitudinal chromatic aberration for incoming visible light in the second wavelength range to less than one diopter while allowing longitudinal chromatic aberration in the first wavelength range in an amount greater than the first diffractive structure.

PRIORITY APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/780,381 filed on May 14, 2010 which claims priority to U.S.provisional application Ser. No. 61/185,510 filed on Jun. 9, 2009, ofwhich the contents of both are incorporated herein by reference.

Related Applications

This application is related to co-pending U.S. patent application Ser.No. 12/780,244 entitled “ZONAL DIFFRACTIVE MULTIFOCAL INTRAOCULAR LENSWITH CENTRAL MONOFOCAL DIFFRACTIVE REGION” claiming priority to U.S.patent application Ser. No. 61/185,512 filed on the same day as theapplication to which the present application claims priority.

BACKGROUND

The present invention relates generally to ophthalmic lenses, and moreparticularly to intraocular lenses (IOLs) that provide compensation forchromatic aberrations.

Intraocular lenses are employed routinely to replace an occluded naturalcrystalline lens via cataract surgery. In other cases, an intraocularlens can be implanted in a patient's eye while retaining the naturalcrystalline lens to improve the patient's vision. Both monofocal andmultifocal IOLs are known. While monofocal IOLs provide a singlefocusing power, multifocal IOLs can provide multiple focusingpowers—typically two—to provide a degree of accommodation, commonlyknown as pseudoaccommodation.

Many conventional IOLs, however, exhibit chromatic aberrations that candegrade their efficiency in concentrating the light energy incidentthereon onto the patient's retina. Nor are such conventional IOLstypically designed to address the chromatic aberrations inherent in thelens and/or present in the optical system of the patient's eye.

Accordingly, there is an ongoing need for enhanced ophthalmic lenses,and particularly IOLs, with improved performance as compared toconventional IOLs.

SUMMARY

In a particular embodiment of the present invention, an ophthalmic lensincludes an optical filter operable to filter out at least visible lighthaving a wavelength less than 450 nm. The lens also includes a firstdiffractive structure adapted to produce a focus for visible light in afirst wavelength range above 550 nm and to reduce longitudinal chromaticaberration to less than one diopter for incoming visible light in thefirst wavelength range. The lens also includes a second diffractivestructure outside the first diffractive structure in a radial directionand adapted to produce a focus for visible light in a second wavelengthrange between 450 nm and 550 nm. The second diffractive structure isalso adapted to reduce longitudinal chromatic aberration for incomingvisible light in the second wavelength range to less than one diopterwhile allowing longitudinal chromatic aberration in the first wavelengthrange in an amount greater than the first diffractive structure.

In another embodiment, a method of manufacturing an IOL includesdetermining a first profile for a first diffractive structure adapted toproduce a focus for visible light in a first wavelength range above 550nm and to reduce longitudinal chromatic aberration to less than onediopter for incoming visible light in the first wavelength range. Themethod also includes determining a second profile for a seconddiffractive structure outside the first diffractive structure in aradial direction and adapted to produce a focus for visible light in asecond wavelength range between 450 nm and 550 nm. The seconddiffractive structure also reduces longitudinal chromatic aberration forincoming visible light in the second wavelength range to less than onediopter while allowing longitudinal chromatic aberration in the firstwavelength range in an amount greater than the first diffractivestructure. The method then includes forming an ophthalmic lens with thefirst profile and the second profile and incorporating an optical filteroperable to filter out at least visible light having a wavelength lessthan 450 nm.

In another embodiment, a method of manufacturing an IOL includesdetermining an optical filter operable to filter out at least lighthaving a wavelength below 450 nm. The method also includes determining afirst profile for at least one central diffractive structure having aradius within a selected pupil size for photopic conditions. The atleast one diffractive structure is configured to correct longitudinalchromatic aberration to less than one diopter in a wavelength rangecorresponding to peak visual receptivity for photopic vision. The methodfurther includes determining a second profile for an optical regionoutside the radius of the first diffractive structure. The opticalregion is configured to allow longitudinal chromatic aberration in anamount greater than the longitudinal chromatic aberration allowed by theat least one diffractive structure. The longitudinal chromaticaberration allowed by the optical region shifts light energy from a peakvisual receptivity for photopic vision toward a peak visual receptivityfor scotopic vision, and the longitudinal chromatic aberration allowedby the optical region is less than one diopter in a wavelength rangecorresponding to the peak visual receptivity for scotopic vision. Themethod then includes manufacturing the ophthalmic lens with the opticalfilter and the first and second profiles for the at least one centraldiffractive region and the optical region.

Further understanding of various aspects of the invention can beobtained by reference to the following detailed description inconjunction with the drawings, which are discussed briefly below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic side view of an IOL in accordance with anembodiment of the invention,

FIG. 1B shows a profile of the anterior surface of the IOL depicted inFIG. 1A from which the base profile of the anterior surface has beensubtracted,

FIG. 2 is a schematic side view of an IOL having multiple diffractivestructures extending to a periphery of the IOL according to anotherembodiment of the invention,

FIG. 3 is a schematic side view of an IOL having an annular refractiveregion separating first and second diffractive structures according toanother embodiment of the invention, and

FIG. 4 is a schematic side view of an IOL in accordance with anotherembodiment of the invention in which the posterior surface of the lensexhibits an aspheric base profile for controlling spherical aberrationseffect,

FIG. 5 is a flowchart illustrating a method of manufacturing an IOLaccording to a particular embodiment of the present invention, and

FIG. 6 is a flowchart illustrating another example method ofmanufacturing an IOL according to a particular embodiment of the presentinvention.

DETAILED DESCRIPTION

The present invention generally provides for an intraocular lens withtwo diffractive structures with a common focus providing chromaticaberration for two different wavelength ranges used in conjunction withan optical filter to limit the spectrum of colors that requirecorrection. A first diffractive structure provides chromatic aberrationcorrection for relatively long wavelengths above 550 nm, while a seconddiffractive structure surrounding the first diffractive structureprovides chromatic aberration correction within a shorter wavelengthrange while allowing chromatic aberration in the longer wavelengthrange. In operation, the combination of diffractive structures providesgood correction for chromatic aberration in small pupil conditions. Theouter diffractive element acts in large-pupil conditions to provideclear images free of chromatic aberration for shorter wavelengths,corresponding to the peak sensitivity of the eye in low-lightconditions. The combination of diffractive elements, along with therestricted spectrum of the light, effectively manages chromaticaberration correction in different wavelength ranges to allow for clearvision under a variety of lighting conditions.

In the embodiments that follow, the salient features of various aspectsof the invention are discussed in connection with intraocular lenses(IOLs). The teachings of the invention can also be applied to otherophthalmic lenses, such as contact lenses. The term “intraocular lens”and its abbreviation “IOL” are used herein interchangeably to describelenses that are implanted into the interior of the eye to either replacethe eye's natural lens or to otherwise augment vision regardless ofwhether or not the natural lens is removed. Intracorneal lenses andphakic intraocular lenses are examples of lenses that may be implantedinto the eye without removal of the natural lens.

FIGS. 1A and 1B schematically depict an intraocular lens (IOL) 10 inaccordance with one embodiment of the invention that includes an optic12 having an anterior surface 14 and a posterior surface 16 disposedabout an optical axis OA. A first diffractive structure 18 is disposedon a central portion of the anterior surface, and is surrounded by asecond diffractive structure 20, which extends from an outer boundary(A) of the monofocal structure 18 to an inner boundary (B) of an outerrefractive region 19 of the anterior surface.

As shown in FIG. 1A, in this embodiment both the anterior surface 14 andthe posterior surface 16 of the IOL 10 have generally convex baseprofiles. In this example, the curvatures of the base profiles of theanterior and posterior surfaces are such that the lens body contributesrefractively to the IOUs far-focus optical power. Further, as notedabove, an outer refractive region 19 of the anterior surface extendsfrom the outer boundary of the second diffractive structure to theperiphery of the lens, which may contribute refractively to a far-focusoptical power for large pupil sizes, e.g., in low light conditions.

Alternatively, the curvatures of the anterior and the posterior surfacescan be selected such that the lens body would contribute refractively tothe lens's near-focus optical power. In other cases, the anterior andposterior surfaces can have substantially flat profiles such that thenear and far-focus optical power of the lens are due to the diffractivecontributions from the first and second diffractive structures with nosubstantial (if any) refractive contribution from the lens body.

The optic can be formed of any suitable biocompatible material,including a plurality of biocompatible polymeric materials. Someexamples of such materials include, without limitation, a soft acrylicmaterial utilized for forming commercial lenses commonly known asAcrysof (a cross-linked copolymer of 2-phenylethyl acrylate and2-phenylethyl methacrylate), silicone and hydrogel. Techniques accordingto the present invention may be particularly suitable for highrefractive index materials over 1.5, which produce significant chromaticdispersion. Suitable optical filters may include materials that can beincorporated into a material proposed for the IOL 10 and may correspondto a range known to improve visual acuity and/or to protect retinaltissue from potentially harmful wavelengths, similar to a naturalcrystalline lens. A suitable material, for example, would be the AcrysofNatural chromophore as described in U.S. Pat. Nos. 5,470,932 and5,543,504, both of which are incorporated herein by reference. Thoughnot shown, the IOL 10 can also include a plurality of fixation members(e.g., haptics) that can facilitate its placement in a patient's eye.

An advantage of certain embodiments of the present invention is that amonofocal IOL may be made thinner than a similar monofocal IOL that ispurely refractive on account of the improved visual acuity fromchromatic aberration correction. To obtain similar performance, a purelyrefractive IOL must have better refractive performance, such as bettercorrection for off-axis and peripheral rays, which ordinarily requiresmore refractive material. The chromatic aberration correction canimprove visual acuity without requiring extensive modifications to therefractive properties of the IOL, which in turn requires less refractivematerial. This may advantageously be exploited to reduce a thickness ofthe IOL in order to permit a smaller incision. Moreover, it provides anadvantage over methods using multiple materials, some having a lowerrefractive index, to correct chromatic aberration, which again increasesthe amount of lens material required.

Another advantage of IOLs of various embodiments of the presentinvention can be a relatively lower diffractive power. In previouslenses that attempted to uniformly correct chromatic aberration over anentirety of the lens for visible wavelengths, the diffractive power hadto be sufficiently high to correct for aberrations even at a peripheryof the lens, which in turn required a high power for the diffractiveelement. Also, as the nominal refractive power of the lens increases,the chromatic aberration becomes correspondingly greater, thus requiringmore diffractive power. According to U.S. Pat. No. 4,655,565 to Freeman,a relatively low-power lens with a nominal power of 12 D would require3.4 D of (negative) diffractive power to produce a net longitudinalchromatic aberration correction of 1 diopter. As the diffractive powerrequired increases, the number of echelettes required also increases,creating a greater likelihood of visual disturbances, such as glare,produced by the diffractive structure.

By way of contrast with prior lenses, various embodiments of the presentinvention allow the diffractive power of both the first diffractivestructure and the second diffractive structure to be less than what isexpected from the teaching of U.S. Pat. No. 4,655,565, thus providingimproved visual performance due to chromatic aberration correctionwithout negative effects that might otherwise be produced by thecorrection. For example, longitudinal chromatic aberration could bereduced to less than a diopter within a central zone with a diffractivepower of 2.39 for the first diffractive structure in a lens with nominalpower of 6 D, a diffractive power of 3.58 with a nominal lens power of21 D, and a diffractive power of 4.56 with a nominal lens power of 34 D.Likewise, the diffractive power of the second diffractive structure,which corrects chromatic aberration within a lower wavelength range, canbe relatively low. For example, longitudinal chromatic aberration withina target range less than 550 nm could be reduced to less than onediopter for a diffractive power of 2.85 D with a nominal lens power of 6D, a diffractive power of 3.58 with a nominal lens power of 4.22 D, anda diffractive power of 8.00 with a nominal lens power of 34 D.

With reference to FIG. 1B, the first diffractive structure 18 includes aplurality of diffractive echelettes 22 separated from one another by aplurality of step heights 24 such that the diffractive structure 18diffracts light into one or more orders. In this example, the stepheights 24 exhibit decreasing heights as a function of increasingdistance from the center of the anterior surface (i.e., the intersectionof the optical axis with the anterior surface). Suitable boundaryconditions can be selected to provide a smooth transition between thefirst diffractive structure 18 and a first echelette 24 c of a seconddiffractive structure. Further details regarding selection of the stepheights in general can be found in U.S. Pat. No. 5,699,142 to Lee etal., which is herein incorporated by reference in its entirety and whichin particular describes apodization of the diffractive pattern in a waythat can reduce glare and/or other negative effects associated withlight at the periphery of the lens. Further details regarding thediffractive correction of chromatic aberration may be found in U.S. Pat.No. 4,655,565 to Freeman and U.S. Pat. No. 5,117,306 to Cohen, both ofwhich are incorporated herein by reference.

The first diffractive structure 18 of the IOL 10 exhibits a negativelongitudinal chromatic aberration. That is, its optical power increaseswith increasing wavelength (its focal length decreases for longerwavelengths). In contrast, the refractive power provided by the IOL 10as well as the human eye exhibit a positive chromatic aberrationcharacterized by a decrease in optical power (increase in focal length)as a function of an increase in wavelength. Hence, the first diffractivestructure can be adapted to compensate for the positive chromaticaberration of the human eye and that of the lens itself for far and/ornear vision. The first diffractive structure 18 is adapted to providecorrection for chromatic aberration for a wavelength range includingwavelengths over 550 nm so as to provide minimal chromatic aberrationover a relatively wide range of visible colors. The first diffractivestructure 18 corresponds to a small pupil size typical of brightlighting conditions. In bright lighting conditions, there is significantsensory response by the visual receptors known as cone cells, which aresensitive to color variations. The visual receptivity of the eye underthese conditions is referred to as “photopic” vision. In particular, thefovea of the human eye, which is responsible for high visual acuity,contains two types of cone cells with peak sensitivity above 550 nm.Thus, in terms of visual acuity, there can be a greater benefit bycorrecting chromatic aberration more stringently, which is to say,providing chromatic aberration correction for a longer wavelength range.The reduction of longitudinal chromatic aberration to less than adiopter over the wavelength ranges described herein is typicallyadequate to provide good visual acuity, so that value will be usedherein as an indication of sufficient correction.

The second diffractive structure 20 also exhibits a negative chromaticaberration correction. The diffractive structures 18 and 20 differ,however, in that the chromatic aberration correction of the seconddiffractive structure 20 allows chromatic aberration to persist at theupper end of the wavelength range to a greater degree than the firstdiffractive structure 18. Thus, for example, the second diffractivestructure 20 may correct chromatic aberration in a range of the filteredlight from 450 nm to 550 nm. Because the second diffractive structure 20is outside the first diffractive structure 18 in the radial direction,the correction in that region corresponds more closely to larger pupilconditions associated with low light. Under these conditions, there istypically insufficient light to trigger the cone cells, meaning thatvision is dominated by the visual receptors known as rod cells havinglimited color sensitivity. The visual receptivity of the eye under theselighting conditions is known as “scotopic” vision. This means that thevisual disturbance from chromatic aberration is less serious, particularfor colors far from the peak sensitivity of the rod cells (around 498nm). The chromatic aberration correction of the second diffractivestructure 20 thus allows more effective transmission of light in thepeak sensitivity area in low-light conditions, which is required forgood visual acuity, while tolerating chromatic aberration forwavelengths that are less important under those conditions.

The described modifications may also be advantageously employed withother modifications pertaining to improved distance vision. For example,the diffractive structures 18 and 20 may be modified so that one focuseslight to a near-vision or distant-vision focus in order to provideimproved visual quality for that range. In low-light conditions wherereading or other near-vision activities are unlikely to take place, morelight energy can be directed to a distant focus by the seconddiffractive structure 20 in order to improve visual acuity in thatrange. Used in conjunction with chromatic aberration correction, theabove IOL 10 can advantageously provide improved distance vision aswell.

In the above embodiments the second diffractive structure 20 istruncated, that is, it does not extend to the periphery of the lens. Inalternative embodiments, a first truncated diffractive structure 18 canbe combined with an outer refractive structure allowing chromaticaberration to produce chromatic aberration correction in a central areaof the IOL 10 while permitting chromatic aberration in an outer regionof the lens. In other alternative embodiments, the second diffractivestructure 20 can extend to the lens's periphery. By way of example, FIG.2 schematically depicts such a lens 46 that includes an optic 48 havingan anterior surface 49A and a posterior surface 49B. Similar to theprevious embodiments, a first diffractive structure 50 is disposed on acentral region of the anterior surface 49A, and is surrounded by asecond diffractive structure 52 that extends from the outer boundary ofthe first diffractive structure to the periphery of the lens. The seconddiffractive structure 52 can include a plurality of diffractiveechelettes that are separated from one another by a plurality of steps,which can have a substantially uniform or apodized heights, e.g., in amanner discussed above. In this case, the step associated with thesecond diffractive structure 52 exhibit decreasing heights as a functionof increasing distance from the center of the anterior surface.

FIG. 3 schematically depicts an IOL 54 according to another embodimenthaving an optic 56 with an anterior surface 58 and a posterior surface60. A first diffractive structure 62 is disposed on a central portion ofthe anterior surface. The anterior surface further includes a seconddiffractive structure 64 that is separated from the first diffractivestructure 62 by an annular refractive region 66. An outer refractiveregion 68 surrounds the bifocal structure.

In some embodiments, a degree of asphericity can be imparted to the baseprofile of the anterior and/or the posterior surface of an IOL so as toameliorate spherical aberrations effects. By way of example, FIG. 4schematically depicts such an IOL 70 that includes an optic 72 having ananterior surface 74 and a posterior surface 76 disposed about an opticalaxis OA. Similar to the previous embodiments, a first diffractivestructure 78 is disposed on a central region of the anterior surface 74while a second diffractive structure 80 in the form of an annular regionsurrounds the first diffractive structure. The base profile of theposterior surface deviates from a putative spherical profile (shown bydashed lines), with the deviation progressively increasing as a functionof increasing distance from the center of the posterior surface definedin this case as the intersection of the optical axis with the posteriorsurface. In some embodiments, the asphericity of the base profile of theposterior surface can be characterized by a conic constant. Theasphericity can change spherical aberrations exhibited by the IOL and/oroffset to some degree a predicted spherical aberration of a cornea.Although in this embodiment the base profile of the posterior surface isadapted to exhibit a degree of asphericity, in other embodiments, suchan asphericity can be imparted to the anterior surface or both surfaces,and diffractive structures 18 and 20 may be superimposed on one or bothsurfaces. It is also possible to have a varying aspheric curvature on anaspheric surface, so that the aspheric profile may be defined by a firstpolynomial within a certain radius and a second polynomial outside thatradius, which can also coincide with a radius of the first diffractivestructure 18 and/or second diffractive structure 20 if desired. The basecurve may also include higher-order asphericity.

FIG. 5 is a flowchart 100 depicting an example method of manufacturingan IOL according to particular embodiments of the present invention. Atstep 102, a limit for filtration of short wavelength light isdetermined. In a typical example, this limit may correspond to a knownoptical filter that can be incorporated into a material proposed for theIOL and may correspond to a range known to improve visual acuity andsimilar to a natural crystalline lens, such as, for example, filteringout light with a wavelength shorter than 450 nm. At step 104, a profilefor a first diffractive structure providing chromatic aberrationcorrection above 550 nm according to any of the various embodimentsdescribed herein, along with any suitable variations that would beapparent to one skilled in the art, is determined. In particular, thedetermination of the first diffractive profile can take into accountdesired power, suitable base curves for the anterior and/or posteriorsurfaces, asphericity or other aberration correction imparted to one orboth surfaces, and the like.

At step 106, a profile for a second diffractive structure providingchromatic aberration correction for a range less than 550 nm whileallowing chromatic aberration for wavelengths greater than 550 nm isdetermined, which may be according to any of the various embodimentsdescribed herein along with any suitable variations that would beapparent to one skilled in the art. In particular, the determination ofthe second diffractive profile can take into account desired power,suitable base curves for the anterior and/or posterior surfaces,asphericity or other aberration correction imparted to one or bothsurfaces, and the like. At step 108, an IOL with the first and seconddiffractive structures having the respective profiles determined insteps 104 and 106 along with an optical filter with the propertiesselected in step 102 is manufactured. Suitable manufacturing techniquesmay include any method of formation suitable to the materials, includingbut not limited to molding, ablating and/or lathing, along with anytechnique for providing an optical filter into the IOL, such asincorporation into the IOL material.

FIG. 6 is another flowchart 200 illustrating an example method ofmanufacturing an IOL according to a particular embodiment of the presentinvention. At step 202, a short wavelength limit for an optical filterof the IOL is determined. At step 204, a profile for a first diffractivestructure is determined. The profile corrects chromatic aberration inorder to maximize light intensity around a peak visual receptivity forphotopic vision. At step 206, a profile for a second diffractivestructure outside the first diffractive structure is determined. Theprofile corrects chromatic aberration in order to maximize lightintensity near a peak visual receptivity for scotopic vision whileallowing chromatic aberration in wavelengths far from peak sensitivity.At step 208, an IOL with the optical filter and the first and seconddiffractive structures is manufactured. Suitable manufacturingtechniques may include any method of formation suitable to thematerials, including but not limited to molding, ablating and/orlathing, along with any technique for providing an optical filter intothe IOL, such as incorporation into the IOL material.

In a variation of the method shown in FIG. 6, the relative area coveredby the first and second diffractive structures can be adjusted to shiftthe visible light energy as between the respective chromatic peaks ofthe diffractive structures. Such adjustments can allow more efficienttransfer of light energy to the respective photopic and scotopic ranges.The adjustments may be analogous to the techniques for shifting lightenergy between foci described in U.S. Pat. Nos. 7,441,894 and 7,481,532to Hong et al., both of which are incorporated herein by reference, butin this case, the energy shift is based on the relative light intensityas a function of wavelength.

In another embodiment, a similar effect can be produced by varying theboundary of the first diffractive structure 18 alone while allowing anouter region that is only refractive, replacing the determination of theprofile for the second diffractive structure with determining arefractive profile outside the first diffractive structure. In such anembodiment, the first diffractive structure 18 still corrects forchromatic aberration in a central region of the IOL for a pupil sizecorresponding to photopic conditions, but the first diffractivestructure 18 is truncated at a certain radius so that, in combinationwith the refractive power, the chromatic aberration from light enteringthe remainder of optic shifts light energy from a peak visualreceptivity for photopic vision to a peak visual receptivity forscotopic vision. The human eye's response for wavelength in the peaksensitivity for scotopic vision tends to be slightly myopic, so theslight shift in power can help to focus light to increase the lightintensity in the wavelength range of scotopic vision. Thus, chromaticaberration need not be corrected for the entire lens. Rather, thechromatic aberration correction needs only provide sufficient correctionfor photopic vision while allowing good scotopic vision in large-pupilconditions when the chromatic aberration of the overall optic is takeninto account. For purposes of this specification, the range for peakvisual sensitivity for photopic vision is 580 nm, plus or minus 30 nm,and the range for peak visual sensitivity for scotopic vision is 505 nm,plus or minus 30 nm.

Those having ordinary skill in the art will appreciate that variouschanges can be made to the above embodiments without departing from thescope of the invention. For example, rather than disposing both thefirst and the second diffractive structures on a single lens surface,one structure can be disposed on the lens's anterior surface and theother on its posterior surface. Additional diffractive structures beyonda first and second diffractive structure may also be included. Further,the base profiles of the anterior and posterior surfaces can beconfigured such that the lens body would contribute refractively to theIOUs near-focus optical power. Such variations and others apparent toone skilled in the art should be understood to fall within the scope ofthe invention as claimed.

1. A method of manufacturing an ophthalmic lens, comprising: determininga first profile for a first diffractive structure adapted to produce afocus for visible light in a first wavelength range above 550 nm and toreduce longitudinal chromatic aberration to less than one diopter forincoming visible light in the first wavelength range; determining asecond profile for a second diffractive structure outside the firstdiffractive structure in a radial direction and adapted to produce afocus for visible light in a second wavelength range between 450 nm and550 nm and to reduce longitudinal chromatic aberration for incomingvisible light in the second wavelength range to less than one diopterwhile allowing longitudinal chromatic aberration in the first wavelengthrange in an amount greater than the first diffractive structure; formingan ophthalmic lens with the first profile and the second profile andincorporating an optical filter operable to filter out at least visiblelight having a wavelength less than 450 nm.
 2. The method of claim 11,wherein a diffractive efficiency of the first diffractive structure is100% for a design wavelength of 580 nm.
 3. The method of claim 11,wherein a diffractive efficiency of the second diffractive structure is100% for a design wavelength of 505 nm.
 4. The method of claim 11,wherein the lens has an overall power up to 6 D and the firstdiffractive structure and the second diffractive structure each have arespective diffractive power less than 3 D.
 5. The method of claim 11,wherein the lens has an overall power up to 21 D and the firstdiffractive structure and the second diffractive structure each have arespective diffractive power less than 4.25 D.
 6. The method of claim11, wherein the optical filter comprises a UV-absorbing material.
 7. Themethod of claim 11, wherein the ophthalmic lens is formed from across-linked copolymer of 2-phenylethyl acrylate and 2-phenylethylmethacrylate.
 8. The method of claim 11, wherein the focus of the firstdiffractive structure coincides with the focus of the second diffractivestructure.
 9. The method of claim 11, wherein the focus of the seconddiffractive structure is a distance-vision focus.